Mana regeneration
The condition of a game character gaining mana points over time is referred to as mana regeneration. Players can gain mana from basically two sources — spirit or items. Spirit regenerates rather high amounts of mana, but suffers from the restriction that it is interrupted for five seconds after spending mana for a spell (see 5 second rule below), while item-based regeneration is usually lower, but continues uninterrupted at all times. Mana regeneration takes place once per tick, but it's usually measured in the amount regenerated every 5 seconds (mp5), because that's the unit used in the tooltips. Spirit-based regeneration The main base stat which regenerates mana is spirit. To a lesser extent, intellect also contributes, and the character level adversely affects regeneration. It's a good rule of thumb to assume that 1 spi = 1 mp5 while not casting. Research by Whitetooth shows that since Patch 2.4 one uniform mana regeneration formula is used across all classes: MP5 = 5 * (0.001 + sqrt(Int) * Spirit * Base_Regen) rounded up Base_Regen is a variable dependent on character level and is summarized in the following table: The above chart was generated using this data. The formula shows that regeneration increases linearly with spirit and with the square root of intellect. The base regeneration goes down as level increases. When analyzing the plot it appears that levels 1-10 have one curve, 11-60 another and 61-70 have a jagged but almost linear decrease which seems to have been tweaked by hand. Together these design elements seem to enforce balanced stats, so that stacking spirit to the detriment of intellect is to be avoided. It seems that 1 spirit = 1 MP5 was the target of the game designers. A level 70 caster needs about 460 intellect to reach this point. Five Second Rule After a character expends mana in casting a spell, the effective amount of mana gained per tick from spirit-based regeneration is reduced (interrupted) for a period of 5 seconds. This is commonly referred to as the five second rule (FSR). Channeled spells are handled a little differently. The FSR starts when the spell's channeling starts; i.e. when mana is expended. The interruption continues for at least five seconds, and longer if the channeled takes more than five seconds. For example, Mind Flay channels for 3 seconds and interrupts regeneration for 5 seconds (from the moment the spell cast starts), while Tranquility channels for 10 seconds and interrupts regeneration for the full 10 seconds, but not longer. By default, the interrupted mana regeneration ratio is 0%. Several effects can increase this ratio, including: * Depending on rank Multiple ratios do stack, but can never exceed 100%. Spells which don't cost mana do not start the FSR. This includes spells with a normal mana cost of zero (e.g. Nature's Swiftness), but also spells whose effective cost is reduced to zero by some effect (e.g. by Clearcasting or an item ability or proc like Eye of Gruul). Prior to Patch 1.4 regeneration was also interrupted during a spells cast time (since then it's only interrupted when mana is expended). For this resaon, in-game textual references to the FSR still read "while casting" where they actually should read "after expending mana to cast". Direct regeneration Many effects increase mana regeneration directly i.e. without increasing spirit. These effects are governed by different rules than spirit-based regeneration, in particular they're never subject to the five second rule. The most frequent source of non-spirit-based regeneration is the "regenerates X mana in 5 seconds" stat on items. This stat is usually written abbreviated as "mp5". There are some effects which regenerate mana (e.g. Insightful Earthstorm Diamond) which deliver their mana the instant they proc. Some items (e.g. Second Wind) do not regenerate mana in 2 second ticks but rather in the intervals actually advertised in their tooltip. Comparing spirit based and direct regeneration In theory, direct regeneration is preferable as it is not subject to the FSR. Unfortunately though, mp5 is much harder to get and more "expensive" than spirit. All attributes have an Item Value, a kind of "cost" associated. This value for mp5 is 2.5 times higher than for spirit. For example the two top mana regeneration enchants for chest items yield either 15 spirit or 6 mp5 ( and ) - this shows the factor of 2.5 very clearly. In order to find out what's better, characters should first find out their personal time spent inside the FSR, e.g using an addon like Muse or RegenFu. It's important to perform the measurement under realistic conditions - the time spent inside the FSR while grinding is typically much lower than during a boss fight. Some players actually argue that in a tight situation, it's safe to assume that the FSR is in effect 100% of the time. It is possible to calculate the percentage of time which has to be spent outside the 5 second rule so that 2.5 points of spirit are more effective than 1 point of mp5. Examples: Average lvl 70 priest with maxed Meditation: 2.5 spirit return 2.5 mp5 outside the FSR, and 0.75 mp5 inside. The mathematical form of the question is thus 2.5 * x + 0.75 * (1 - x) = 1 1.75 * x = 0.25 x = 0.14 So if that priest spends 14% percent of the time outside the FSR, the enchant with 15 spirit yields a higher regeneration than 6 mp5. If the time inside the rule is 86% or more, 6 mp5 is more efficient. For lvl 70 characters without spirit regeneration inside the FSR: 2.5 * x = 1 x = 0.4 That is they have to spend 40% of their time outside the rule for spirit to be better than mp5. MP5 vs Intellect and Spirit - Formulas The following formulas relate intellect, spirit, and mp5 to mana regen both in and out of FSR in an attempt to help establish a relative value between them depending on your current stats. Based on the formulas for spirit-based regeneration above... ManaRegen(Int,Spirit,MP5) = + sqrt(Int) * Spirit * 0.005575 * 5 + MP5 ManaRegenCasting(Int,Spirit,MP5) = + sqrt(Int) * Spirit * 0.005575 * 5 * Coeff + MP5 where Coeff is the decimal percentage of spirit-based mana regeneration that is allowed to continue while casting The mana regen benefit per 1 point increase of Spirit, Intellect, or Mana/5 can be calculated as... While not casting: NC_RegenPerInt = 0.027875 * Spirit * - sqrt(Int) NC_RegenPerSpirit = 0.027875 * sqrt(Int) NC_RegenPerMP5 = 1 While casting: C_RegenPerInt = Coeff * NC_RegenPerInt C_RegenPerSpirit = Coeff * NC_RegenPerSpirit C_RegenPerMP5 = 1 As you can see, MP5 is the only stat whose effect remains constant both in and out of casting. If you have no talents allowing mana to regenerate from spirit while casting, MP5 is the only way to do so. Even with them, MP5 is still quite valuable, given the most common of these effects (listed above) cap at 30% spirit-based regeneration. References Additional notes * Mana regeneration is not affected by sitting down or standing up * Spell casting never stops direct mana regeneration effects from items * Spell casting does not in itself have an effect on regeneration, only mana expenditure * Maximum direct MP5 from item buffs and armor enchants in 3.0.3 is 114 (Flask of Pure Mojo38, Exceptional Mana Oil19, Mighty Rhino Dogs16/Spicy Fried Herring16, Arcanum of Blissful Mendinghead, Greater Inscription of the Cragshoulder, Prophetic Auraleg, Magister's Armor Kithands, Enchant Chest - Greater Mana Restoration8, Enchant Boots - Greater Vitality6, Enchant Bracer - Restore Mana Prime6). External links * Resto4Life.com has an extensive discussion of mana regeneration — complete with a Javascript-driven mana regeneration calculator — all of which is up to date with the changes in 2.4. * An in-game version of the above calculator can be found at Curse Category:Formulas and game mechanics